Optical coherence tomography difference maps and average macular volume for geographic atrophy

Nano-enhanced Optical Gene Delivery to Retinal Degenerated Mice

BACKGROUND

The efficient and targeted delivery of genes and other impermeable therapeutic molecules into retinal cells is of immense importance for the therapy of various visual disorders. Traditional methods for gene delivery require viral transfection, or chemical methods that suffer from one or many drawbacks, such as low efficiency, lack of spatially targeted delivery, and can generally have deleterious effects, such as unexpected inflammatory responses and immunological reactions.

METHODS

We aim to develop a continuous wave near-infrared laser-based Nano-enhanced Optical Delivery (NOD) method for spatially controlled delivery of ambient-light-activatable Muti-Characteristic opsin-encoding genes into retina in-vivo and ex-vivo. In this method, the optical field enhancement by gold nanorods is utilized to transiently permeabilize cell membrane, enabling delivery of exogenous impermeable molecules to nanorod-binding cells in laser-irradiated regions.

RESULTS AND DISCUSSION

With viral or other non-viral (e.g. electroporation, lipofection) methods, gene is delivered everywhere, causing uncontrolled expression over the whole retina. This will cause complications in the functioning of non-degenerated areas of the retina. In the NOD method, the contrast in temperature rise in laser-irradiated nanorod-attached cells at nano-hotspots is significant enough to allow site-specific delivery of large genes. The in-vitro and in-vivo results using NOD, clearly demonstrate in-vivo gene delivery and functional cellular expression in targeted retinal regions without compromising the structural integrity of the eye or causing immune response.

CONCLUSION

The successful delivery and expression of MCO in the targeted retina after in-vivo NOD in the mice models of retinal degeneration opens a new vista for re-photosensitizing retina with geographic atrophies, such as in dry age-related macular degeneration.

Near-Infrared Laser-Based Spatially Targeted Nano-enhanced Optical Delivery of Therapeutic Genes to Degenerated Retina

Non-viral delivery of therapeutic genes into targeted areas of retina is essential for re-functionalizing the retinal circuitry. While a focused ultrafast laser beam has been recently used for intra-ocular delivery of molecules, it poses the significant technical challenge of overcoming aberrations of the eye and maintaining a tightly focused spot on the retinal cell membrane. Furthermore, to minimize collateral damage and increase the throughput of gene delivery, we introduced a weakly focused near-infrared (NIR) continuous wave (CW) or pulsed laser beam on to the cells wherein the intensity is locally enhanced by gold nanorods bound to the cell membranes to permit gene insertion. Parametric optimization of nano-enhanced optical delivery (NOD) was carried out by varying the exposure time, as well as the power of the CW NIR beam or the energy of the pulsed NIR beam. Using this NOD method, therapeutic genes encoding for multi-characteristic opsins (MCOs) were delivered to spatially targeted regions of degenerated retina ex vivo as well as in vivo. NOD-mediated cell membrane-specific expression of MCOs in targeted retinal regions with photoreceptor degeneration will allow functional recovery in an ambient light environment.

Associations Between β-Peripapillary Atrophy and Reticular Pseudodrusen in Early Age-Related Macular Degeneration

Purpose

Choroidal thinning has been associated with reticular pseudodrusen (RPD) and β-peripapillary atrophy (β-PPA), which have been linked to normal-tension glaucoma (NTG). This analysis sought to determine whether RPD are independently associated with β-PPA in early AMD patients. Secondary outcomes included the association of RPD and preexisting diagnosis of glaucoma, cup-to-disc ratio (CDR), subfoveal choroidal thickness (SFCT), and IOP.

Methods

This prospective cross-sectional study examined 78 age- and sex-matched early AMD patients: 43 RPD patients (63 eyes) and 35 non-RPD patients (64 eyes). Exclusion criteria included advanced AMD, high myopia, and vitreoretinal conditions/surgery. RPD and non-RPD groups were identified by confocal scanning laser ophthalmoscopy. β-PPA as well as CDR were graded on digital, nonstereoscopic fundus photos. SFCT was measured on spectral-domain optical coherence tomography for 69 patients (35 RPD and 34 non-RPD). IOP and glaucoma diagnosis were extracted from charts.

Results

β-PPA had a greater prevalence in RPD than non-RPD (44% vs. 19%, P = 0.002); however, this relationship was not significant when SFCT was added to the model (P = 0.150). A preexisting diagnosis of glaucoma (P = 0.156), CDR (P = 0.176), and IOP (P = 0.98) was not different between groups.

Conclusions

RPD in early AMD are associated with presence of β-PPA, but choroidal thickness is a confounder in this relationship. Because β-PPA is a common finding in NTG, focusing on a potential shared pathway between RPD and NTG could improve the understanding of pathophysiology and expand therapies for each condition.

Impact of retinal pigment epithelium pathology on spectral-domain optical coherence tomography-derived macular thickness and volume metrics and their intersession repeatability

BACKGROUND

To determine the impact of retinal pigment epithelium (RPE) pathology on intersession repeatability of retinal thickness and volume metrics derived from Spectralis spectral-domain optical coherence tomography (Heidelberg Engineering, Heidelberg, Germany).

DESIGN

Prospective cross-sectional single centre study.

PARTICIPANTS

A total of 56 eyes of 56 subjects were divided into three groups: (i) normal RPE band (25 eyes); (ii) RPE elevation: macular soft drusen (13 eyes); and (iii) RPE attenuation: geographic atrophy or inherited retinal diseases (18 eyes).

METHODS

Each subject underwent three consecutive follow-up macular raster scans (61 B-scans at 119 μm separation) at 1-month intervals.

MAIN OUTCOME MEASURES

Retinal thicknesses and volumes for each zone of the macular subfields before and after manual correction of segmentation error. Coefficients of repeatability (CR) were calculated.

RESULTS

Mean (range) age was 57 (21-88) years. Mean central subfield thickness (CST) and total macular volume were 264 and 258 μm (P = 0.62), and 8.0 and 7.8 mm³ (P = 0.31), before and after manual correction. Intersession CR (95% confidence interval) for CST and total macular volume were reduced from 40 (38-41) to 8.3 (8.1-8.5) and 0.62 to 0.16 mm³ after manual correction of segmentation lines. CR for CST were 7.4, 23.5 and 66.7 μm before and 7.0, 10.9 and 7.6 μm after manual correction in groups i, ii and iii.

CONCLUSIONS

Segmentation error in eyes with RPE disease has a significant impact on intersession repeatability of Spectralis spectral-domain optical coherence tomography macular thickness and volume metrics. Careful examination of each B-scan and manual adjustment can enhance the utility of quantitative measurement. Improved automated segmentation algorithms are needed.